If you like doing things yourself and making sure, then ja open them up now and do them with Corrosion block. If you can reseal them, that's cool, but if not, no problem either. You can inspect them so much easier without seals.

Ceramic Abec 5 bearings available from Smoothdrag.com USA. Ceramic bearings last longer than Stainless, but are more expensive and sometimes noisier. There is no discernible feeling difference between stainless and Ceramic. You won't notice a difference.